1. Field of the Invention
This invention pertains to an improved article of manufacture that is intended for use in controlling the passage of radiant energy for such uses as glazing or the like.
2. Background and References
"Diode glazing" is a transparent glazing that allows incident radiant energy to pass freely in the incoming direction, but allows very little radiation or conduction heat transfer to pass in the opposite direction. Diode glazing is a thin, light weight, transparent material that can be used in nearly any glazing application in which it is desirable to allow transmission of incident radiation and to suppress radiation and conduction heat transfer in the opposite direction, over a wide band of radiation wave lengths, including radar, infrared, visible light, and ultraviolet wavelengths.
For example, in a greenhouse or solar collector, it is desirable to have a glazing which allows as much as possible of the incident sunlight to pass inside, but which minimizes the radiation, convection and conduction heat loss to the outside. Ordinary glass is naturally transparent to sunlight but is somewhat opaque to infrared radiation of longer wavelength emitted from within the greenhouse, so ordinary glass naturally acts as a partially effective radiation diode or trap. This effect is called "the greenhouse effect."
In the past some features related to diode glazing (glazing that allows incident radiant energy to pass freely in the incoming direction, but that opposes radiation or conduction heat transfer in the opposite direction) have been described.
U.S. Pat. No. 4,053,327 to Meulenberg describes a cover for photovoltaic cells which refracts incident sunlight away from opaque electrical conductor grid lines and onto active cell areas in order to improve performance. This cell cover is designed for flat-plate, non-concentrating photovoltaic cells.
U.S. Pat. No. 4,307,711 to Doundoulakis describes a tracking solar collector with an array of light focusing elements to provide a linear array of focused light that passes through small glass covered apertures in an evacuated insulated tube finally to be absorbed on a heat exchanger tube.
U.S. Pat. No. 4,323,053 to McCullough et al. describes a transparent honeycomb glazing for solar collectors which is intended to act as a heat trap glazing, as a result of the greenhouse effect. The honeycomb cells of still air are also intended to provide thermal resistance to heat losses from within the solar collector.
U.S. Pat. No. 4,412,528 to Elzinga describes a double-pane window with fluorescent material on strips between the panes to absorb and re-emit radiation which is then transferred by total internal reflection to a heat storage means at one edge of the window. The window is intended to collect and store solar heat for useful purposes.
U.S. Pat. No. 4,711,972 to O'Neill describes a solar energy collector for converting concentrated solar energy into electricity through the use of photovoltaic cells. O'Neill also includes a photovoltaic cell cover for enhancing the performance of photovoltaic cells. The cell cover concentrates radiant energy into the active region of the photovoltaic cells and eliminates the losses that normally occur when radiant energy falls on the opaque electrical conductor grid lines of the photovoltaic cells.
None of the patents described above provide collection and trapping of incident radiant energy by the use of reflectors or by a combination of lenses and reflectors, nor do they provide thermal resistance to radiation and conduction heat losses. Neither have any previous technical articles been found which provide such features. Accordingly, there is a need for an improved glazing material that can provide these features and thus improve the efficiency of glazing used on greenhouses, solar collectors, passive solar buildings, natural lighting of buildings, and IR signature suppression applications.